Coated fabrics

ABSTRACT

multi-ply An elastomer coated, open weave, square woven fabric of milti-ply cords including continuous filament, organic, synthetic fibers, in which both the cords and their component plies have a twist in the range of 3 1/2 to 45 turns per inch.

O United States Patent [151 3,661,692 B rczi [451 May 9, 1972 54] COATED FABRICS 3,470,836 /1969 New et a1... ..57/140 x 3,373,774 3/1968 Cruz ....139/426 X [721 Charles Ormsklrk, England 3,113,886 12/1963 KOlb ..161 /88 x [73] Assignee: Deering Milliken Research Corporatio 2,971,321 2/1961 Himmelfarb et a1. ..57/ 140 X Spartanberg, C, 2,939,200 6/1960 Ewing et a1. 161/89 X 2,893,442 7/1959 Genin ..139/383 [221 mm 1968 2,739,919 3/1956 Artzt ..161/89 x [21] Appl.No.: 816,849 2,143,574 1/1939 Porter et a1. ..139/426 X Primary .\-aminerRobert F. Burnett Forelgn Apphcauon Pmmty Data 1 Assistant Examiner-Mark A. Litman Nov. 25, 1968 Great Britain ..53,619/67 Atto ey-Norman C. Armitage and H. William Petry Nov. 25, 1968 Great Britain ..53,620/67 [57] ABSTRACT [52] 11.8. C1 ..l61/89, 161/90, 161/92,

l6l/95 57/140 139/420 139/426 multi-ply An elastomer coated, open weave, square woven 51 1111.01. ....D03d 15/00,B3 2b 27/02 fabric miltiply including filament 58] Field of Search 57 /1 140 139/426 383 ganic, synthetic fibers, in which both the cords and their com- 4 l61/88 93 pOnent plies have a twist in the range of'3 V2 to turns per inch. [5 6] References Cited 18 Claims, N0 Drawings COATED FABRICS The present invention relates to a new fabric which is of particular use in the manufacture of Hovercraft skirts.

Hovercraft skirts are generally made of fabric coated with neoprene rubber or natural rubber and this coated fabric has to withstand very rapid and violent flexing, and so the adhesion between the rubber and the fabric is of particular importance. It is particularly difficult to obtain adhesion that is strong enough to withstand this usage for long. Further, the coated fabric of a Hovercraft skirt has to be resistant to the action of sea-water, sand and stone rubble and this places further demands on the fabric.

Fabric at present used for Hovercraft skirts is generally a nylon fabric of fairly conventional structure which has been treated with isocyanate (to provide adhesion) and covered with neoprene or natural rubber. The bonding between the nylon and the rubber is not entirely satisfactory and normally the use of isocyanate is undesirable as isocyanate compounds generally are toxic.

A fabric according to the present invention is an open weave woven fabric of multi-ply cords, in which both the cords and their component plies are of high twist. By high twist we mean a twist of at least 3% turns per inch, although higher twists e.g., at least 5 turns per inch and up to e.g., 45 turns per inch can often be used to advantage.

The number of ends and picks per inch in the fabric is normally in the range of 4 to 50. Preferred values are between and 25. In general the higher is the weight of the cord per unit length the lower is the number of picks and ends per inch. The fabrics may be square-woven, if they have substantially the same number of ends and picks per inch, but minor deviations from this square woven construction are possible. For example there may be up to about 20 percent and preferably not more than 10 percent more picks than ends, or vice versa. As an example a fabric might have ends per inch and 17 picks per inch.

Generally a similar cord is used for both the warp and the weft. The cord may comprise two or more plies of yarn but twoand three-ply cords are preferred. The direction of twist in the yarns is preferably opposite to the direction of twist in the cord. Desirably the twist in the cord is such that the yarn filaments lie mainly along the axis of the cord since we have found that this imparts high flex fatigue life to the fabric. By stating that the yarn filaments preferably lie mainly along the axis of the cord we mean that the angle between the yarn filament and the axis of the cord is generally less than 15 although, greater angles e.g., up to 45, can also be used sometimes with very satisfactory results. Most preferably, however the yarn filaments are substantially parallel with the cord axis. In a two-ply cord this result may be achieved by using approximately the same number of turns per inch for both the yarns and the cord, whilst for cords having three or more plies it may be achieved by using a higher twist for the yarns than for the cords, in both cases the twist direction in the yarns being opposite to that in the cord.

If more than three plies are employed it is preferred that the cord should be built up by twisting a number of twoor threeply cords together. Thus a strong four-ply cord may be obtained by twisting two two-ply cords with their twists in opposite directions.

It is often preferred that both the yarns and the cord should have a twist in the range of 6 to 13, and preferably 8 to 13 turns per inch although higher twists e.g., up to 17, 20, or even more, turns per inch are occasionally advantageous since, for

a given material the lighter the yarn the higher the yarn and cord twists must be in order to obtain a fabric having a long flex fatigue life.

The yarns are preferably made of synthetic organic continuous filament materials, such as rayon, nylon, polyester and polypropylene although glass or cotton yarns may also be used. The denier of the yarns is normally at least 210 and examples of preferred yarns are 840 and 1260 denier nylon and 1000 denier polyester.

The fabrics need to be of an open weave since they are designed to be coated with elastomer ultimately, as in the manufacture of Hovercraft skirts. An open weave permits good strike through of the elastomer so that after vulcanization of the elastomer coating there is good elastomer to elastomer adhesion, and thus good adhesion of the elastomer to the fabric.

By the term openweave we mean that preferably at least 2 percent, more preferably at least 5 percent, of the fabric area is void space. Generally the area of void space is less than 67 percent, preferably not more than 50 percent, of the fabric area. The area of void space is preferably in the range of 5-30 percent of the fabric area. Often the breadth of the spaces between pairs of adjacent weft of warp cords or, in the case of a matt weave, the spaces between adjacent groups of warp or weft cords, in the fabric is of the order of the diameter of the cords, e.g., at least half the diameter of the cords. Apart from the fact that an open weave assists good adhesion of elastomer coatings to the fabrics, it is also desirable in that it tends to result in increased tear strength and flexibility. These properties are of particular importance in material for Hovercraft skirts.

We have made fabrics in which the tear strength is more than half the tensile strength and such high ratios of tear strength to tensile strength are very valuable in materials for Hovercraft skirts since they mean that high tear resistance can be achieved without the use of very heavy fabrics. We believe that the high twist of the cords of the fabrics and of the component plies of the cords is also an important factor in producing high tear strength and high flexibility.

The fabrics often have a plain weave but in some cases other types of weave e.g., a matt weave may be advantageous. Where a plain weave is used the number of ends and picks per inch is preferably lower than for a matt weave e.g., a 2/2 matt weave using the same cord material. This is so since'a matt weave is inherently more open than a corresponding plain weave and thus to obtain a given degree of openness with the latter less picks and ends per inch must be used. Naturally this means that for a given degree of openness and using the same cord material a higher tensile strength can be achieved by a matt weave than by a plain weave.

Fabrics according to the invention can readily be made having a tensile strength (before coating) of at least 200, often between 250 and 1,000, lbs. or even higher, for example up to 5,000 per l-inch strip in both warp and weft directions. For a given material the tensile strength depends on the yarn material being used and on the weight per unit area of the fabric, which, in turn depends on the weight of the cord per unit length and on the number of ends and picks per inch.

The fabrics according to the present invention are very suitable for use in Hovercraft skirts and for this purpose must be coated with an elastomer. Such elastomer coated fabrics may be made by applying a suitable adhesive to the fabric and subsequently applying a layer of elastomer to the adhesive coated fabric, e.g., by calendering or spread coating. An alternative method which has been used for coating fabrics with elastomer involves forming an adhesive system comprising resorcinol, a formaldehyde donor, e.g., hexamethylene tetramine and a silica reinforcing filler, mixing this with an elastomer and calendering or spread coating the resultant mixture onto the fabric.

In general, we prefer to coat the fabrics with a composition comprising an adhesive resin and a latex of an elastomer and then to apply the elastomer coating, the elastomers of the latex and coating being the same or at least being highly compatible. However certain adhesive compositions containing no latex have also been found to be satisfactory. The adhesive compositions may be applied in the form of a dip to the fabrics, and are preferably applied under pressure, thus forcing the adhesive into the center of the thickness of the fabric. For example they may be applied by the use of padding mangles. Instead of applying an adhesive composition to the woven fabric an adhesive composition may be applied to the cords of the fabric before weaving.

Examples of adhesive resins of use in adhesive compositions containing a resin and an elastomer include precondensed, partially pre-condensed or even uncondensed resorcinol-formaldehyde resins (these being strongly preferred), mixtures of resorcinol-formaldehyde resin and one or more amino silanes,

order to pre-shrink it'or, more conveniently, by heating the cords of the fabric or their component yarns before the fabric mixtures of resorcinol-formaldehyde and epoxy resins, mixtures of resorcinol-formaldehyde, amino silane and blocked isocyanate, mixtures of epoxy resin and blocked isocyanate, mixed resorcinol-formaldehyde and epoxy resins with blocked isocyanate, and polyurethanes. The resins may be introduced in the form of solvent solutions, emulsions or liquid dispersions into the adhesive compositions. When blocked isocyanates are used these may be unblocked after application of the adhesive composition to the fabric. Unblocked isocyanates can also be used but tend to be toxic and not to give as good bonding as the adhesives described above.

Latices which may be used in the adhesive compositions include those of natural rubber, sytrene-butadiene rubber, Neoprene rubber, PVC,vinyl-pyridine-styrene-butadiene terpolymer rubber and nitrile and butyl rubbers. Generally the elastomer of the adhesive composition is chosen so as to be the same as the elastomer of the coating subsequently to be applied over the adhesive, sometimes however use of one type of elastomer in the adhesive composition gives good adhesion for a subsequently applied different type of elastomer coating, e.g., a coating of Hypalon rubber is bonded well by use of an adhesive composition comprising neoprene.

After application of the adhesive compositions the coated fabric is dried without any substantial curing, e.g., by heating to the temperature of 230 F. The elastomer coating can then be applied to the adhesive coated fabric e.g., by hot calendering sheets of the elastomer onto the adhesive coated surfaces or by applying it in paste form on a spread coating machine followed by drying. Finally the coated material is vulcanized e.g., by heating at 300 F.

The coating of elastomer applied to the fabric may be one of natural rubber of of a synthetic, elastomer e.g., styrene-butadiene, neoprene, nitrile, ethylene-propylene, Viton, Hypalon, P.V.C, polyvinylidene chloride and polyurethane elastomers. Blends of two or more such elastomers may also be used. In some cases the two sides of the fabric may be coated with different types of elastomer. This may be useful for material for Hovercraft skirts where different parts of the skirts are subjected to widely differing conditions, the outward facing part of the material, for example, being subject to the effect ofsunlight. Neoprene or natural rubber are generally preferred at present. For parts of a Hovercraft skirt exposed to particularly severe abrasion, .poly urethane and P.V.C. coatings have been found to be very useful.

The coated fabrics may be cut and shaped into the desired form and fitted to a Hovercraft as any part of the skirt (including the fingers) in any suitable manner. They are found to be very wear resistant, and, particularly on larger Hovercraft, have a life very much greater than has been obtained with known fabrics.

The non-square woven fabrics used in Hovercraft skirts according to the present invention permit the construction of Hovercraft skirts having direction-dependant properties and this is advantageous since the skirts may be subject to more strain in some directions that in others. The skirts may be made by cross-laminating more than one coated fabric, the angle between successive laminae often being substantially 90. The use of cross-laminated non-square woven fabrics is of value since choice of the angle of cross-lamination enables fabrics with particular directional characteristics to be constructed. In particular by choice of the angle of cross-lamination the flexibility of the fabric in a given direction can be controlled. Furthermore cross-lamination is of use in increasing the tear strength of the fabric in a particular direction.

Certain fabric materials e.g., nylon, shrink on heating and this means that shrinkage of the fabrics is likely to occur when the applied adhesive composition is dried and when the coated material is vulcanized. We find that problems associated with shrinkage may be avoided by heating the original fabric in is woven. By use of sufficiently high temperatures, e.g., about 430 F. in the case of nylon fabrics, shrinkage in subsequent stages can be virtually eliminated. Preferably the temperature used for pre-shrinking is above the temperature employed for vulcanization after an elastomer coating has been applied. Such heating has the additional advantage of setting the twist in the yarns and cords although the twist setting could be effected, and sometimes is, by heating at lower temperatures e.g., 220 F. The pre-shrunk cords which may be obtained as described above may be treated with the adhesive composition before being woven into the fabric.

For certain applications it may be desirable to laminate the fabrics according to the invention after'applying the adhesive and elastomer and in such laminates the warp and weft cords of one fabric layer may be at right angles or at smaller angles to the warp and weft cords of another fabric layer.

The invention is further described with reference to the following examples.

EXAMPLE I A fabric having 17 ends and 17 picks per inch was woven in a 2/2 matt weave from 'warp and weft 3-ply cords of 1260 denier nylon yarn. The yarns had a twist of 93/4 turn per inch and the 3-ply cords had a twist of 9% turns per inch and the 3- ply cords had a twist of 8 turns per inch. The fabric so made had a weight of 20 ounces per square yard and a tensile strength of 1000 lbs. for a l-inch strip.

EXAMPLE 2 A fabric was woven from the same cord as in Example 1 in a plain weave with 13% ends and 13% picks per inch. The fabric weighed 15 ozs. per square yard and had a tensile strength of 750 lbs. per l-inch stn'p.

EXAMPLE 3 A fabric having 23 ends and 23 picks per inch was woven in a 2/2 matt weave from two-ply cords of 840 denier nylon yarns. Both the yarns and the cord had a twist of 12 turns per inch. The fabric had a weight of 10% ozs. per square yard and a tensile strength of 600 lbs. per one inch strip.

EXAMPLE 4 A fabric having 17 ends and 17 picks per inch was woven in a plain weave from the same cord as that of Example 3. The fabric had a weight of 7% ounces per square yard and had a tensile strength of 400 lbs. per one inch strip.

EXAMPLE 5 A fabric having 20 ends and 20 picks per inch was woven in a plain weave from two-ply cords of 420 denier nylon yarns. Both the yarns and the cords had a twist of 17 turns per inch. The fabric weighed 4% ounces per square yard and had a tensile strength of 200 lbs. per l-inch strip.

Another suitable fabric has a warp and weft of two-ply 1260 denier nylon 66, with 9% turns singles and 9% turns ply twbt per inch and has 13 ends and 13 picks per inch, whilst another suitable fabric has warp and weft of three-ply 1260 denier nylon 66 with 9% turns singles and 8 turns p1y twist per inch v and has 10 ends and 10 picks per inch.

EXAMPLE 6 A fabric having 20 ends and 12 picks per inch was woven in a plain weave from warp and weft two-ply cords of 840 denier nylon. The yarns had a twist of 12 turns per inch and the cords a twist of 12 turns per inch. EXAMPLE 7 Adhesive dips were prepared as given below, applied by means of a padding mangle to fabrics according to the invention and the dipped fabrics then dried by heating at 230 F. Sheets of Neoprene rubber were then hot calendered onto the dipped fabrics and the product vulcanized by heating at 300 F. In each case the rubber coated fabric was found to have high tear strength and high flexibility, and the adhesion of the rubber coating was found to be excellent.

A partially pre-condensed resol type adhesive resin was prepared by pre-condensing the following for 2 hours at 65 F: 476.6 parts by weight of water 3.0 parts by weight of sodium hydroxide,

22.0 parts by weight of resorcinol, and 32.4 parts by weight of 37 percent by weight aqueous solution of formaldehyde. Various dips were prepared by mixing this pre-condensate with one or more latices. Vinylpyridine-styrene-butadiene terpolymer and/or styrene-butadiene latices were also included in some of the dips. The dip compositions are shown in Table l in which all parts and percentages are by weight. The resorcinol-formaldehyde resin in the Table is that described above, Pliolite latex VP-lOO is a vinylpyridine-styrene-butadiene terpolymer latex filamems of the individual and Pliolite latex 2108 tadiene latex.

is a cold polymerized styrene-buan adhesive composition prior to being coated with the elastomer.

3. A fabric according to claim 1 in which the cords have been treated with an adhesive composition before weaving, but after any pre-shrinking by heating.

4. A fabric according to claim 1 in which both the cords and their component plies have a twist in the range of 5 to 45 turns per inch.

5. A fabric according to claim 1 in which, in the cords, the plies lie mainly along the axial direction of the cords.

6. A fabric according to claim 1 in which the cords are of TABLE 1 1 2 3 4 5 Mix Diy Wet Dry Wet Dry Wet Dry Wet Dry Wot Neoprene lulox 750 (50%) 100.0 200. 0 150. 0 300.0 200. 0 400.0 100.0 00.0 100.0 200. 0 lllolitc latvx \P. 100 (41%) 100.0 243.9 50. 0 122. 0 100.0 243. 9 50.0 122. 0 Ilmliw latex 2108 (40%) 50. 0 125. 0 R oscol'cinol-l'ornmldehyde rosin- 37. 0 534. 0 37. 0 534. 0 37. 0 534. 0 37. 0 534; 0 37. 0 534. 0 Zmc oxltlu dispersion (509;v 15. 0 30.0 20.0 40. 0 30.0 60.0 7.5 15.0 15.0 30.0 Totals 252. 0 1,007. 0 257. 0 996. 0 267. 0 904. 0 244. 5 902. 1) 252.0 1,011.0 Total solids, percent 25. 2 25. 8 26. 9 24. 6 25.0 The dips were prepared by mixing the ingredients in three plies. h M 0 in order given and, in each case, were allowed to stand for 7. A fabric according to claim 1 in which each cord consists several hours before application to the fabrics, the zinc oxide of two-or three-ply cords twisted together. being added just prior to use. The dips, were very stable and 8. A fabric according to claim 1 in which the plies are of could be stored for a long time. nylon.

EXAMPLE 8 9. A fabric according to claim 2 in which THE adhesive An adhesive dip was prepared as given below, applied by composition comprises an adhesive resin and an elastomer. means of a padding mangle to fabries a cording t the i ve 10. A fabric according to claim 9 in which the elastomer is a tion and the resulting fabrics dried by heating. Sheets of natufubbef- D ral rubber were then hot calendered onto the adhesive coated A fabric accordmg tot-131m 9 which the elastomer fabrics and vulcanized. The fabrics so obtained had high tear D strength, high flexibility and the adhesion of the rubber was A fabnc accordmg to clam 9 1h wh'ch the adhesive excellent resin is a resorcinol-formaldehyde resin.

The dip, comprising a novolak type i l f l 13. A fabric according to claim 9 coated with an elastomer dehyde resin was made by dissolving 2.0 parts of caustic soda which is the sfmle as h in the adhesive Composition in 64.5 parts of water. To the solution 36.0 parts by weight of fabnc accordmg to clam 9 f wnh 'f 75 percent by weight catalin 779 resin was added separately which 15 different from an elastomer in the adhesive composianother mix consisting of 31.4 parts of water and 20.0 parts by weight of 37 percent by weight formaldehyde was made The 15 fabric according to claim 1 in which the elastomer dip was made up by adding the resin mix followed by the forcoatmg naFural rubher or 9 i maldehyde mix to one or more latices as given in Example 16. A fabric according to claim havmga tensile strength in The dip was allowed to stand several hours before application. the range of ZOO-SD00 per l'mch Smp m both warp and what we claim is: weft directions.

1. An elastomer coated open weave square woven fabric of A accordmg g g has been premulti-ply cords including continuous filament organic shrunk by hetmg the m e synthetic fibers, in which both the cords and their component A accordmg to C alm 17,whlch has been plies have a twist in the range of 3% to 45 turns per inch. shrunk by heatmg the cords before weavmg' 2. A fabric according to claim 1 which has been treated with 

2. A fabric according to claim 1 which has been treated with an adhesive composition prior to being coated with the elastomer.
 3. A fabric according to claim 1 in which the cords have been treated with an adhesive composition before weaving, but after any pre-shrinking by heating.
 4. A fabric according to claim 1 in which both the cords and their component plies have a twist in the range of 5 to 45 turns per inch.
 5. A fabric according to claim 1 in which, in the cords, the filaments of the individual plies lie mainly along the axial direction of the cords.
 6. A fabric according to claim 1 in which the cords are of two or three plies.
 7. A fabric according to claim 1 in which each cord consists of two-or three-ply cords twisted together.
 8. A fabric according to claim 1 in which the plies are of nylon.
 9. A fabric according to claim 2 in which THE adhesive composition comprises an adhesive resin and an elastomer.
 10. A fabric according to claim 9 in which the elastomer is a rubber.
 11. A fabric according to claim 9 in which the elastomer is P.V.C.
 12. A fabric according to claim 9 in which the adhesive resin is a resorcinol-formaldehyde resin.
 13. A fabric according to claim 9 coated with an elastomer which is the same as an elastomer in the adhesive composition.
 14. A fabric according to claim 9 coated with an elastomer which is different from an elastomer in the adhesive composition.
 15. A fabric according to claim 1 in which the elastomer coating is natural rubber or neoprene rubber.
 16. A fabric according to claim 1 having a tensile strength in the range of 200-5,000 lbs. per 1-inch strip in both warp and weft directions.
 17. A fabric according to claim 1 which has been pre-shrunk by heating the material of the fabric.
 18. A fabric according to claim 17, which has been pre-shrunk by heating the cords before weaving. 